The Dry Tropospheric Correction is not received via a direct Auxiliary Data File (ADF) input. Instead this correction is computed by the CryoSat processors using dynamic mean surface pressure Meteo grids sourced from Meteo-France via the Systeme au Sol d'ALTimetrie et d'Orbitographie (SSALTO) based on the European Centre for Medium-Range Weather Forecasts (ECMWF) model, as well as static S1 and S2 tide grids of monthly means of global amplitude and phase. These static tide grids for amplitude and phase have latitude coverage from -90 to +90 degrees and a step in latitude/longitude of 1.125 degrees.

For the Dry Tropospheric Correction over water (open water, semi-enclosed seas or enclosed seas and lakes), the surface pressure is equal to the mean pressure minus the climatology (computed with the pressure grids). Over land, the surface pressure is equal to the mean pressure so the Dry Tropospheric Correction over land is computed from the mean pressure alone.

The Wet Tropospheric Correction is provided by Meteo grids, sourced from Meteo-France via SSALTO and is based on the ECMWF model. The Wet Tropospheric Correction is received as a direct ADF input from ECMWF analysed grids and is then formatted to the CryoSat Payload Data Segment (PDS) file standard before being used in CryoSat data processing.

More detailed information on the geophysical corrections used in the processing of the Level 2 CryoSat data products in provided in the L2 Geophysical Corrections document.